Simple field weakening control for permanent magnet stepper motors without dq transformation

In this paper, a simple field weakening control (FWC) without direct quadrature (DQ) transformation is proposed for position tracking of permanent magnet stepper motors (PMSMs). The proposed method consists of the PID controller for a torque modulation and a commutation scheme to achieve FWC without DQ transformation. In proposed commutation scheme, the desired negative direct current is designed to cancel the back-emf so that the required inputs can decreased. The commutation scheme is equivalent to microstepping where currents have time-varying amplitude over 0.5π electrical phase advance. For simple implementation, proportional integral (PI) current feedback was used to guarantee the desired current. Simulation results validate the performance of the proposed method.